1. Field of the Invention
With the widespread usage of electrospray ionization techniques the atmospheric pressure ionization/mass spectrometer has become the most widely accepted device for chemical analysis. The present invention is also usable in those instances where thermospray ionization is still found to be functionally adequate. Atmospheric pressure interfaces have been used for many different types of mass spectrometers wherein charged droplets are formed in an atmospheric pressure electrospray ionization source which are then transported to a mass spectrometer analyzer through a capillary inlet. Most commercial devices utilize a single electrospray device in conjunction with a singular nozzle. Multiple electrospray needles, or ESI sprayers, have been used to enhance nebulization. Also use of dual ESI sprayers have been tried with a Y-shaped orifice defined within the nozzle in order to investigate electrosprayed proteins using ion-ion or ion-molecule reactions. In particular the accurate measurement of masses of organic compounds has been another use of this system for the purposes of avoiding suppression of the sample by the reference. Standard dual ESI sprayers have also been used in various configurations of mass spectrometer manufacturers. It is important, however, to know that the present invention is particularly novel since only one nozzle has been used heretofore and the spraying mists are mixed prior to entering the first stage of pumping. Automation of the accurate measurement of multiple organic and biological compounds using electrospray ionization has become increasingly important. Double-focusing mass spectrometers have very high resolution and have been used to confirm the chemical composition of organic compounds. However, the more modern time of flight mass spectrometer has been used for chemical composition analysis most recently especially due to their lower cost when compared to double-focusing units. High resolution of the sector instruments is an important factor for achieving high mass accuracy by resolving peak interferences. However, when dealing with the analysis of complex mixtures long scan times used by the sector instrument may not be compatible with the narrow peaks generated under micro and capillary high performance liquid chromatography and capillary electrophoresis. Recent advances in the commonly available configurations of the time-of-flight mass spectrometers have made it possible to acquire complete spectra with adequate resolution during a very short time period. These advances in the time-of-flight mass spectrometer, as well as their lower cost, when compared to double focusing mass spectrometers makes their usage in automated analysis much more cost feasible. The concept of present invention, however, is clearly less expensive and more beneficial using any type of mass spectrometer and is not contemplated to be restricted to only time-of-flight mass spectrometer configurations. The present invention does provide a means for simultaneously measuring multiple fluid sample inputs in a mass spectrometer that is particularly advantageous when utilizing the time-of-flight mass spectrometer.
2. Description of the Prior Art
Numerous prior art devices have been designed in the spectrometer field for enhancing analytical techniques such as shown in U.S. Pat. No. 3,112,639 patented Dec. 3, 1963 to C. T. Maxwell and assigned to Beckman Instruments, Inc. on a xe2x80x9cDual Column Gas Chromatograph And Method For Analysisxe2x80x9d; and U.S. Pat. No. 3,119,251 patented Jan. 28, 1964 to M. A. Bowers and assigned to Standard Oil Company on a xe2x80x9cMultiple Column Gas Chromatographyxe2x80x9d; and U.S. Pat. No. 3,236,603 patented Feb. 22, 1966 to L. R. Durrett et al and assigned to Shell Oil Company on a xe2x80x9cMultiple-Column Gas Chromatographic Apparatusxe2x80x9d; and U.S. Pat. No. 3,449,563 patented Jun. 10, 1969 to H. W. Brown and assigned to Varian Associates on a xe2x80x9cSample Insertion Probe Having Integral Sample Introduction Control Means And Mass Spectrometer Means Using Samexe2x80x9d; and U.S. Pat. No. 3,578,969 patented May 18, 1971 to W. Proskauer and assigned to Electronic Associates Inc. on a xe2x80x9cSolid Sample Inlet System For A Mass Spectrometerxe2x80x9d; and U.S. Pat. No. 3,590,243 patented Jun. 29, 1971 to R. Perrin et al and assigned to Avco Corp. on a xe2x80x9cSample Insertion Vacuum Lock And Probe Assembly For Mass Spectrometersxe2x80x9d; and U.S. Pat. No. 3,800,602 patented Apr. 2, 1974 to A. W. Jones and assigned to Hooker Chemical Corporation on a xe2x80x9cMulti-Stream Gas Chromatographic Method And Apparatusxe2x80x9d; and U.S. Pat. No. 3,916,465 patented Nov. 4, 1975 to A. W. Jones and assigned to Hooker Chemicals and Plastics Corporation on a xe2x80x9cMulti-Stream Gas Chromatographic Method And Apparatusxe2x80x9d; and U.S. Pat. No. 3,933,047 patented Jan. 20, 1976 to P. Fowler and assigned to Cabot Corporation on a xe2x80x9cMethod And Means For Gas Sampling In Mass Spectrometryxe2x80x9d; and U.S. Pat. No. 4,035,168 patented Jul. 12, 1977 to W. G. 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Ligon et al and assigned to General Electric Company on an xe2x80x9cAdjustable Open-Split Interface For A Gas Chromatograph And A Mass Spectrometerxe2x80x9d; and U.S. Pat. No. 5,311,016 patented May 10, 1994 to E. Villa-Aleman and assigned to The United States of America as represented by the United States Department of Energy on an xe2x80x9cApparatus For Preparing A Sample For Mass Spectrometryxe2x80x9d; and U.S. Pat. No. 5,345,079 patented Sep. 6, 1994 to J. B. French et al and assigned to MDS Health Group Limited on an xe2x80x9cApparatus And Method For Liquid Sample Introductionxe2x80x9d; and U.S. Pat. No. 5,360,976 patented Nov. 1, 1994 to D. T. Young et al and assigned to Southwest Research Institute on a xe2x80x9cTime Of Flight Mass Spectrometer, Ion Source, And Methods Of Preparing A Sample For Mass Analysis and Of Mass Analyzing A Samplexe2x80x9d; and U.S. Pat. No. 5,400,665 patented Mar. 28, 1995 to J. Zhu et al and assigned to Cetac Technologies Incorporated on a xe2x80x9cSample Introduction System For Inductively Coupled Plasma And Other Gas-Phase, Or Particle, Detectors Utilizing An Enclosed Filter Solvent Removal System, And Method Of Usexe2x80x9d; and U.S. Pat. No. 5,426,301 patented Jun. 20, 1995 to P. turner on an xe2x80x9cOff-Axis Interface For A Mass Spectrometerxe2x80x9d; and U.S. Pat. No. 5,449,902 patented Sep. 12, 1995 to K. Onishi et al and assigned to Hitachi, Ltd. and Takeda Chemical Industries, Ltd. on an xe2x80x9cApparatus For Directly Coupling Analytical Column With Mass Spectrometerxe2x80x9d; and U.S. Pat. No. 5,504,326 patented Apr. 2, 1996 to J. Reilly et al and assigned to Indiana University Foundation on a xe2x80x9cSpatial-Velocity Correlation Focusing In Time-Of-Flight Mass Spectrometryxe2x80x9d; and U.S. Pat. No. 5,508,204 patented Apr. 16, 1996 to E. J. Norman and assigned to Norman Clinical Laboratories, Inc. on a xe2x80x9cMultiple Sample Sequential Chemical Analysisxe2x80x9d; and U.S. Pat. No. 5,510,613 patented Apr. 23, 1996 to J. Reilly et al and assigned to Indiana University Foundation on a xe2x80x9cSpatial-Velocity Correlation Focusing In Time-Of-Flight Mass Spectrometryxe2x80x9d; and U.S. Pat. No. 5,526,682 patented Jun. 18, 1996 to J. A. Jarrell et al and assigned to Waters Investments Limited on a xe2x80x9cMethod And Apparatus For Analyzing Sample Solutionsxe2x80x9d; and U.S. Pat. No. 5,565,677 patented Oct. 15, 1996 to A. S. Wexler et al and assigned to The University of Delaware on an xe2x80x9cAerodynamic Nozzle For Aerosol Particle Beam Formation Ink To A Vacuumxe2x80x9d; and U.S. Pat. No. 5,574,277 patented Nov. 12, 1996 to S. J. Taylor and assigned to Graseby Dynamics Limited on an xe2x80x9cIntroduction Of Samples Into An Ion Mobility Spectrometerxe2x80x9d; and U.S. Pat. No. 5,580,430 patented Dec. 3, 1996 to S. H. Balagopal et al and assigned to Ceramatec, Inc. on a xe2x80x9cSelective Metal Cation-Conducting Ceramicsxe2x80x9d; and U.S. Pat. No. 5,597,467 patented Jan. 28, 1997 to J. Zhu et al and assigned to Cetac Technologies Inc. on a xe2x80x9cSystem For Interfacing Capillary Zone Electrophoresis And Inductively Coupled Plasma-Mass Spectrometer Sample Analysis Systems, And Method Of Usexe2x80x9d; and U.S. Pat. No. 5,661,038 patented Aug. 26, 1997 to J. T. Brenna et al and assigned to Cornell Research Foundation, Inc. on an xe2x80x9cInterface System For Isotopic Analysis Of Hydrogenxe2x80x9d; and U.S. Pat. No. 5,633,496 patented May 27, 1997 to M. Sakairi et al and assigned to Hitachi, Ltd. on a xe2x80x9cMass Spectrometry Apparatusxe2x80x9d; and U.S. Pat. No. 5,643,800 patented Jul. 1, 1997 to E. R. Tarantino et al and assigned to Hewlett-Packard Company on a xe2x80x9cMethod Of Preparing A Sample For Analysis By Laser Desorption Ionization Mass Spectrometryxe2x80x9d; and U.S. Pat. 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The present invention provides an improved mass spectrometer apparatus which can be used to analyze numerous fluid samples simultaneously. It includes a detector apparatus for monitoring fluid samples moving therewithin for providing analytical information thereon such as mass or charge. The detector apparatus also defines a detector inlet therein adapted to receive fluid samples. The detector apparatus preferably is a time-of-flight mass spectrometer which facilitates analyzing of different fluid samples passing therethrough in parallel relation to one another at a high speed and at minimal cost. Use with other types of mass spectrometers other than the time-of-flight design is also contemplated under this invention.
The apparatus further includes a quadrupole ion guide positioned in fluid flow communication with the detector and adapted to guide the movement of fluid samples thereinto for analysis. The quadrupole ion guide also defines a guide inlet for receiving fluid sample for analysis and a guide outlet in fluid flow communication with respect to the detector inlet in order to guide movement of the fluid sample thereinto. The quadrupole ion guide includes a guide pump in fluid flow communication therewith which is adapted to reduce the air pressure therein to a level of approximately 20 millitorr. The quadrupole ion guide may also include a supplemental pumping apparatus to facilitate maintaining of the 20 millitorr air pressure level. A skimmer may also be included positioned over the guide inlet of the quadrupole ion guide to facilitate movement of fluid sample in parallel with respect to other fluid samples into the quadrupole ion guide.
A nozzle is used configured with a plurality of sampling orifices extending therethrough to facilitate parallel entry of multiple fluid samples simultaneously through the skimmer. The sampling orifices are isolated from one another within the nozzle to prevent mixing of fluid samples passing therethrough. In this manner each of the sampling orifices will define an individual sampling inlet and sampling outlet which are in fluid flow communication together through its respective sampling orifice. The sampling inlets of the sampling orifices within the nozzles are preferably spatially separated from one another by a sufficient distance to prevent mixing of the unique fluid samples introduced into each of the sampling inlets. The nozzle orifices are preferably angularly oriented with respect to one another in such a manner that they converge at the sampling outlets thereof. In this configuration the spatial separation between the sampling outlets is less than the spacing between the sampling inlets. Preferably sampling orifices are configured with an internal diameter sufficiently small in order to maintain the desired low pressure level within the primary reduced pressure chamber. This design consideration is particular advantageous to maintain low pressure levels in the chamber when multiple channels are used.
A nozzle heating device is also included which is operative to heat the nozzle preferably to a temperature of approximately 150 degrees Centigrade to facilitate the movement of fluid sample therethrough. A sample housing is also included which defines a primary reduced pressure chamber therewithin. The sampling housing includes a sample pump designed to reduce the air pressure therein to approximately five torr in order to facilitate fluid sample movement therethrough. The nozzle is preferably positioned extending through the sample housing into the primary reduced pressure chamber with each of the sampling outlets thereof positioned within the primary reduced pressure chamber to be exposed to an environment of below atmospheric pressure and with each of the sampling inlets positioned external to the sampling housing to be exposed to ambient atmospheric pressure.
The guide pump is operative to reduce the air pressure within the quadrupole ion guide to a level well below the atmospheric pressure and also below the level within the primary reduced pressure chamber. A fluid introduction device is also operatively positioned adjacent to each of the sampling inlets of the nozzle means in an environment of ambient atmospheric pressure to separately provide fluid sample to each of the sampling inlets while minimizing mixing therebetween. This fluid introduction means preferably includes a plurality of electrospray ionization spray devices each of which is associated with one of the sampling inlets such that each individual device is adapted to receive a different and unique fluid sample and provide it to the sampling inlet without any mixing therebetween.
It is an object of the present invention to provide an improved mass spectrometer apparatus which is operative to analyze multiple fluid samples concurrently wherein cost is minimized by utilizing a time-of-flight spectrometer detector apparatus.
It is an object of the present invention to provide an improved mass spectrometer apparatus which is operative to analyze multiple fluid samples concurrently wherein the number of moving parts are minimized to limit down time.
It is an object of the present invention to provide an improved mass spectrometer apparatus which is operative to analyze multiple fluid samples concurrently wherein reliability is significantly enhanced.
It is an object of the present invention to provide an improved mass spectrometer apparatus which is operative to analyze multiple fluid samples concurrently wherein multiple streams of different unique fluid samples are maintained almost completely separated with virtually no mixing to facilitate analysis thereof by a time-of-flight mass spectrometer detector apparatus.
It is an object of the present invention to provide an improved mass spectrometer apparatus which is operative to analyze multiple fluid samples concurrently wherein samples can be received from various types of input sources such as liquid chromatography or capillary electrophoresis or syringe pumps.
It is an object of the present invention to provide an improved mass spectrometer apparatus which is operative to analyze multiple fluid samples concurrently wherein one of the sampling orifices can be used to introduce a reference compound to facilitate accuracy in measurement.
It is an object of the present invention to provide an improved mass spectrometer apparatus which is operative to analyze multiple fluid samples concurrently wherein the sample analysis time is greatly decreased due to the parallel analysis of multiple samples.
It is an object of the present invention to provide an improved mass spectrometer apparatus which is operative to analyze multiple fluid samples concurrently wherein costs are minimized by allowing a plurality of different samples to be analyzed simultaneously.
It is an object of the present invention to provide an improved mass spectrometer apparatus which is operative to analyze multiple fluid samples concurrently wherein adaption to spectrometers already in the field can be upgraded with minimal modifications thereby eliminating the high cost of purchasing new instruments.
It is an object of the present invention to provide an improved mass spectrometer apparatus which is operative to analyze multiple fluid samples concurrently wherein the problems associated with multiple nozzle orifices such as the increase in internal pressure at the nozzle housing and the quadrupole ion guide can be overcome by the use of supplemental devices.
It is an object of the present invention to provide an improved mass spectrometer apparatus which is operative to analyze multiple fluid samples concurrently wherein individual electrospray ionization devices can be utilized with one for each individual unique fluid sample.
It is an object of the present invention to provide an improved mass spectrometer apparatus which is operative to analyze multiple fluid samples concurrently wherein interaction between the individual samples and between the samples and any reference compound utilized is minimized.
It is an object of the present invention to provide an improved mass spectrometer apparatus which is operative to analyze multiple fluid samples concurrently wherein the current low cost of time-of-flight mass spectrometers as compared to double focusing mass spectrometers is a distinctive cost advantage.
It is an object of the present invention to provide an improved mass spectrometer apparatus which is operative to analyze multiple fluid samples concurrently wherein interference is minimized by utilizing multiple ESI sprayers.